if not here are the steps: 1. downlaod sdk source base 2007 by going to your library, click tools, there should be a list of stuff, scroll down and find "sdk source base 2007"2. go to the black mesa official website (google it) and click downloads, download by torrent, it's way better3. when downloaded, click the installer, install it, it should take a really long time.4. when its done, restart steam and BOOM, it's in your library5. Enjoy the game and never sleep 'till you finish it